Flat Cover

Abstract

A removable flat cover is frequently utilized as the main closure for the tubeside chamber in tubular heat exchangers. In fact, of the five front end styles shown in the TEMA Standards (ref. Table 1.3.1), three contain removable bolted flat covers. Removing a bolted cover does not involve disconnecting channel connections, and the required removal space can be quite small. The cover can be hung from a “davit” or a “hinge” (Photograph 12.a) attached to the mating flange, which can facilitate cover removal. Instead of a davit, a hydraulic or air operated hinge and door set up may be used. These attributes make removal of the cover perhaps the most expeditious way to gain access to the tube-to-tubesheet joint for tube cleaning or for tube plugging operations. In applications involving expensive alloys for the tubeside material, a carbon steel flat cover is easily faced with a liner of the required alloy material thus yielding savings in the hardware cost. Finally, the circular shape makes the flat cover one of the simplest pressure vessel shapes to analyze for pressure loadings. Rules for flat cover design have appeared since early editions of the ASME Boiler and Pressure Vessel Codes. The ASME Code rules are intended only to limit the maximum stress level in the cover.